The Dublin actor will join the likes of Diane Lane, Imogen Poots, Juliana Canfield and Lashana Lynch in the pilot adaptation for FX, written by Michael Green (who co-wrote the screenplay for 'Blade Runner 2049', 'Logan' and others.)
The comic book series, written by Brian K. Green, has been hugely successful and critically acclaimed since launching in 2002 and follows the fortunes of Yorick Brown - the last human on earth with a Y chromosome - and his sidekick, a monkey called Ampersand. Brown is an escape artist who is on a quest to find out why a mysterious global plague wiped out the male Y chromosome - and why he may, indeed, be the last surviving man on the planet.
Poots will play his sister, Hero, while Lane will play his mother, a US senator.
According to FX: "Y traverses a post-apocalyptic world in which a cataclysmic event has decimated every male mammal save for one lone human. The new world order of women will explore gender, race, class and survival."
Keoghan will next be seen in HBO series 'Chernobyl' opposite Jared Harris.
So, how d'you feel about monkeys, Barry?